POS0894 DIFFERENTIAL DIAGNOSIS BETWEEN HAND OSTEOARTHRITIS AND PSORIATIC ARTHRITIS USING INDOCYANINE GREEN-BASED FLUORESCENCE OPTICAL IMAGING
Authors: B. Drude, Ø. Maugesten, S. G. Werner, J. Berger, J. Klotsche, G. R. Burmester, I. K. Haugen, S. Ohrndorf
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Fluorescence optical imaging (FOI) provides a measure of inflammation in finger joints and wrists [1,2]. Recognizing specific joint signals and morphologic patterns in FOI may be helpful in differential diagnosis of hand osteoarthritis (OA) and psoriatic arthritis (PsA). <h3>Objectives</h3> To analyze the diagnostic value of the established FOI Activity Score (FOIAS) and predefined morphologic patterns in the differentiation between hand OA and PsA. <h3>Methods</h3> FOIAS has been validated for inter- and intra-reader reliability[3]. FOI sequences were examined by one trained reader (BD). Cases with physician-based diagnosis of hand OA (n=47) and PsA (n=54) were randomly mixed and the reader was blinded to diagnosis. In total, 16 joints (wrist, thumb base, MCP1-5, (P)IP1-5, DIP2-5) in each hand were evaluated on a semiquantitative 0-3 scale in five images during the FOI sequence (composite image PrimaVista Mode (PVM), phase 1, phase 2 (first and middle image), and phase 3). Additionally, predefined morphologic patterns were observed ('streaky signals'[2], 'green/blue nail sign'[4], 'Werner sign'[1,5] and 'bishop's crozier sign'[3]). A collection of example images for joint signals and morphologic findings was previously compiled into an atlas for reference and training[3]. Based on joint signals and morphologic findings, the reader matched each case to diagnosis OA or PsA. Agreement on diagnosis was calculated using Cohen's kappa (κ). Mean sum signals for different joint groups were compared by T test for independent samples. Morphologic pattern distribution was assessed with Pearson Chi-Square. <h3>Results</h3> 78.2% of cases (79/101) were diagnosed correctly by reading FOI, showing moderate agreement (κ=0.57, p&lt;0,001). For PIP2-5, we found overall statistically significantly higher mean joint sum scores in OA cases (39.0 in OA vs. 20.0 in PsA, p&lt;0.001) as well as for each of the 5 phases (PVM, phase 1, phase 2 first and middle, phase 3). DIP2-5 displayed overall statistically significantly higher mean joint sum scores in OA (16.5 in OA vs. 8.4 in PsA, p&lt;0.001) as well as in PVM, phase 2 first and middle images. Other joint groups (MCP1-5, wrist) did not present any statistically significant differences between OA and PsA. Regarding morphologic patterns, the 'Werner sign' was presented significantly more often in PsA patients (55.6% in PsA vs. 21.3% in OA, p&lt;0.001). <h3>Conclusion</h3> There was moderate agreement between the physician-based diagnosis of OA and PsA and the diagnosis that was proposed based on FOI findings. OA cases presented more pronounced signal enhancement in PIP and DIP joints when compared to PsA cases. Additional morphologic criteria and pattern recognition might be needed to expand the diagnostic capability of FOI. <h3>References</h3> [1]Werner SG, Langer HE, Ohrndorf S, et al. Ann Rheum Dis. 2012 Apr;71(4):504-510 [2]Glimm AM, Werner SG, Burmester GR, et al. Ann Rheum Dis. 2016 Mar;75(3):566-570 [3]Drude B, Maugesten Ø, Werner SG, et al. Ann Rheum Dis. 2021;80:983 [4]Wiemann O, Werner SG, Langer HE, et al. J Dtsch Dermatol Ges. 2019 Feb;17(2):138-148 [5]Zeidler H 2019. Fluoreszenzoptische Bildgebung. In: Zeidler H, Michel BA. Differenzialdiagnose rheumatischer Erkrankungen 5. Aufl. Springer, Heidelberg, S. 88-89 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Benedict Drude: None declared, Øystein Maugesten: None declared, Stephanie Gabriele Werner: None declared, Jörn Berger Employee of: Xiralite GmbH, Jens Klotsche: None declared, Gerd Rüdiger Burmester: None declared, Ida K. Haugen Grant/research support from: Pfizer/Lily (paid to institution) and personal fees from Abbvie, Novartis and GSK, outside of the submitted work, Sarah Ohrndorf: None declared